Reinforced propeller



March 21, 1944. Q E;` JAWS'ON 2,344,876

REINFORCED PROPELLER Filed April 6, 1942 A a) 20d ffm @g f@ 4f?./m/W/"mwz larney.

Patented Mar. 21, 1944 UNITED REINFORCED PROPELLER Clarence B. Jamison,Beverly Hills, Calif., assignor of twenty per cent to Collins Mason,Beverly Hills, Calif.

Application April 6, 1942, Serial N0. 437,740

Claims. (Cl. Uli- 173) My invention has to do with propellers and, inits more particular aspects, it relates to nonmetallic blades forairplane propellers embodying novel means for strengthening the bladeshanks and for retaining such blades in metal hubs.

While wood has many desirable qualities as material for airplanepropellers, two major problems have prevented wood blades from beinglargely used in metal hubs such as are employed to enable the pitchangle of the blades to be adjusted or controlled. One of thoseshortcomings has been that the relative weakness, in essential respects,of Wood as compared with metal has rendered it necessary to employ bladeshanks of such large diameter as to require inordinately large and heavyhubs to mount them. This problem is easy to understand when oneconsiders the relatively weak tensile strength of Wood and contemplatesthe tremendous centrifugal forces of many tons as well as other stressesexerted on a propeller blade shank in operation. Another shortcoming hasbeen the dilculty of positively and safely retaining the blade shanks inthe hubthat is, to avoid throwing of the blades.

I have overcome those difliculties by incorporating in the blade shank anovel reinforcing element of relatively stronger material, such asmetal, in such manner as to cause the tensile stresses normally appliedto the weakest section of the blade shank to be transferred to andshared by the strongest section of the blade.

I am aware that attempts have been made heretofore to provide metalreinforcement for wood blades, but those attempts have been unsuccessfulfrom a practical standpoint. One of the contributing reasons for thelack of success of those prior attempts has been due to the fact thatthe inherent nature of the two materials, wood and metal, rendered itimpossible to obtain adequate bonding of the laminae. This has made itnecessary to extend the metal reinforcing throughout the major part ofthe length of the blade and even then the tendency has been for the woodto pull away from the reinforcing.

It is among the objects of my invention to provide a non-metallicpropeller blade such as Wood incorporating a novel reinforcing memberand means of mounting it in the blade shank, which provides maximumstrength for minimum crosssectional area and which is at the same timeextremely economical of manufacture and light in Weight.

Another object is the provision of improved means for retaining anon-metallic blade in a metal hub.

Still further objects and corresponding advantages are inherent in myinvention and how those as well as the foregoing objects are achievedwill be made clear to those skilled in this art by the followingdetailed description of one of the preferred forms which my inventionmay take, for which purpose I shall refer to thev accompanying drawing,in which:

Fig. 1 is a longitudinal section taken on Vline I-I of Fig. 3; l

Fig. 2 is a longitudinal section on line 2--2of Fig. 3;

Fig. 3 is a cross-section taken on line 3- -3 of' Fig. 1; and

Fig. 4 is a cross-sectional view of the blade shank showing the relationof the laminae prior to being compressed together. 4

In the drawing, the numeral 5 designates a propeller hub consisting oftwo oppositely disposed halves providing a longitudinal bore' to receivethe propeller shank assembly to be described, each half presenting ateach end bosses provided with holes to receive bolts 6 for clamping thehub halves about the propeller 'shank assembly. r

The numeral l0 generally indicates a propeller blade having a shankportion ll, the blade tapering from the relatively smaller shankportion'to an adjacent airfoil portion I2 of relatively greaterdiameter. l

Shank portion ll tapers from its inner and outer endsto a reduceddiameter central section l5 and is made up of Wood laminae lla, lib andl lc securely bonded together in superposed relation by a suitablebonding agent. While I show a shank made up of rive laminae, this numberis by no means critical and any desired number of laminae may be used.Preferably, however, there should be an odd number so that there may bea central lamina for the purpose now tol be described.

As best shown in Figs. 1,v 2 and 3, the central shank lamina l la isrelatively narrower than the outwardly adjacent laminae YI lb, isseparated from the corresponding lamina I Id which extends into theairfoil portion of the blade, and terminates short of the inner end ofthe shank, so that a channel or recess is formed entirely around thecentral shank lamina ll a. Within this recess I place a metal insertgenerally designated 2li which is in the form of a somewhat rectangularframe having sides 20a extending longitudinallyof the shank, inner end20h and outerv end 20c, which ends extend transversely vof the shank.-Sides 20a converge inwardly towards the center, conforming to the hourglass-shaped plan section of the shank.

As shown in Fig. 4, central laminae Ha, Hd are preferably maderelatively thicker than the metal insert 2li-that is, they arerelatively thicker before being compressed in the course of applyingpressure to bond the glued laminae into a substantially integral mass-sothat the metal insert will not prevent proper compressing of the centralwood laminae Ila, lld. The centrai shank lamina may be considered asbeing comprised of the metal insert and the wood lamina Ha as a core,the latter fitting snugly into the frame-'like insert.

Shank II as thus composed is compressed within a split sleeve which inturn is threaded into a ferrule 32, the latter having annular flanges32a, 32D tting corresponding recesses in the hub.

The diametrically opposite longitudinal splits 35 which divide sleeve 30into two segments, are preferably circumferentially spaced from theinsert 20 so that the outer tapered surface of the insert bears againstthe correspondingly shaped inner surface of the sleeve at pointsvremoved from .the splits.

The inner surface .31 of the outer end portion of the ferrule tapers toconform to the enclosed outer surface .33 of the blade Vadjacent theshank, so that relative rotation of the ferrule 'with respect `to the.sleeve `will cause the tapered inner surface 40 of the sleeve tocompress the correspondingly tapered 4portion of the shank and insert,and will cause the tapered surface 3l `of the ferrule to-compress theportion 38 of the blade, thus venabling such adjustment as will at al1times maintain .a tig-ht t regardless of :any shrinkage.

From the :foregoing description, it will be seen that `the relativelysmall area of the wood shank displaced by the metal insert 2i) sosubstantially increases thestrengthof the structure that wood bladesvhaving Shanks Yof relatively small crosssection comparable with metalblades may be used, and at the same time the method of constructing theblade is so simple as to vprovide great economy in manufacture.Centrifugal forces tending to pull the shank 4longitudinally from thesleeve are taken directly by the metal insert and are therebydistributed evenly throughout the Wood :shank section by virtue of thecore Ha being integrated by a firm bond with the remainder Aof theshank. inasmuch as the outer transverse portion 29e of the metal insert-is within the relatively larger and stronger section of the blade, thestresses are also taken by that larger and stronger blade portion.

I preferably provide the opposite faces `of the metal insert 20 withoutwardly projecting barbs laminae llb when compressed together, thusfurther aiding the integration of the shank elements.

I nd it highly advantageous to taper the shank I l as well as thereinforcing member sides 20a from their outer ends towards the center,in conformance with the taper of the adjacent inner surface of thesleeve, because it permits a gradual reduction in the section of .theshank rather than .an abrupt reduction, which .latter wouldsubstantially increase the breaking moment at the point of reduceddiameter.

While I have specifically referred to wood blades, it will be understood.of course that my invention also contemplates other non-metallicblades, such .as plastic blades and Iplastic-impregnated wood blades,and While I preferably employ aluminum as the metal of the insert 20, Imay employ `other suitable metals.

The broad concept of my invention, as dened by the appended claims, ofcourse may be carwhich become embedded in the adjacent ried out instructures varying from that herein specifically described, so that thedetails which I have hereinbefore employed to illustrate an adaptationof my invention are not be taken as limitative.

1. In a propeller, a hub having a radial socket, a blade having alaminated shank mounted in the socket, the centermost lamina of theshank comprising a relatively narrow center strip bonded to adjacentlaminae and a reinforcing plate having a side portion extending alongthe side edge of the center strip and a portion eX- tending transverselyof the shank between the center strip and the outer end of the blade,and means in the hub embracing the shank, said means engaging the sideportion of .the reinforcing plate and constricting the outer laminae ofthe shank .against opposite faces of the reinforcing plate.

2. In a propeller, a hub having a radial socket, a Vblade having alaminated shank mounted in the socket yand tapering from its inner endto a reduced vdiameter medial portion, the centermost lamina of theshank comprising a relatively narrow center strip bonded to adjacentlaminae and a reinforcing member having side portions extending alongthe opposite side edges of the center strip and converging towards theshank portion of reduced diameter, and means in the hub engaging theouter side edges of the reinforcing member and constricting the outerlaminae of the shank against opposite faces of the .rein-forcing member.

3. The propeller of claim 2 wherein the reinforcing member includes aweb extending transversely .of the shank between the center strip andthe outer portion of the blade, said web being connected to the sideportions of the reinforcing member.

4. In an airplane propeller of the class clescribed, a metal hub, anon-metallic blade having a shank, said shank tapering from its innerend to a reduced diameter portion, a longitudinally split sleeveembracing the shank and mounted in the hub, and a metallic reinforcingmember having end portions extending transversely through the shank andside portions extending longitudinally along opposite sides of theshank, said sides being embedded in and conforming to the longitudinalsectional shape of the shank and bearing at their outer side edgeportions against the inner surface of the sleeve.

5. In an airplane propeller of the class described, a metal hub, anon-metallic blade having a shank composed of superposed laminae thecentermost of which is comprised of a center strip and a metalreinforcing member extending transversely through the shank andlongitudinally thereof along opposite side edges of the center stripwith its outer side edges flush with the adjacent outer side surface ofthe shank, said shank tapering from its inner end to a reduced diametermedial portion, and a longitudinally split sleeve mounted in the hubsurrounding and embracing the shank, said center strip being bonded atits opposite side faces to the adjacent laminae whereby to preventlongitudinal movement of the reinforcing member with respect to theshank.

CLARENCE B. JAMISON.

